High selectivity, low stress, and low hydrogen diamond-like carbon hardmasks by high power pulsed low frequency rf

ABSTRACT

Provided herein are methods and related apparatus for depositing an ashable hard mask (AHM) on a substrate by pulsing a low frequency radio frequency component at a high power. Pulsing low frequency power may be used to increase the selectivity or reduce the stress of an AHM. The AHM may then be used to etch features into underlying layers of the substrate.

INCORPORATED BY REFERENCE

A PCT Request Form is filed concurrently with this specification as partof the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed PCT Request Form is incorporated by reference hereinin its entirety and for all purposes.

BACKGROUND

Amorphous carbon films may be used as hard masks and etch stop layers insemiconductor processing, including in memory and logic devicefabrication. These films are also known as ashable hard masks (AHMs)because they may be removed by an ashing technique. As aspect ratios inlithography increase, AHMs require higher etch selectivity. Currentmethods of forming highly selective AHMs using plasma enhanced chemicalvapor deposition (PECVD) processes result in AHMs with high stress,limiting the AHMs' usefulness as hard masks. Accordingly, it isdesirable to produce AHMs having high etch selectivity, but low stress.

Background and contextual descriptions contained herein are providedsolely for the purpose of generally presenting the context of thedisclosure. Much of this disclosure presents work of the inventors, andsimply because such work is described in the background section orpresented as context elsewhere herein does not mean that it is admittedto be prior art.

SUMMARY

Disclosed herein are methods and systems of depositing an ashable hardmask (AHM) film by plasma enhanced chemical vapor deposition (PECVD)that decreases stress levels and increases etch selectivity. In variousembodiments, the methods can involve exposing a substrate to a processgas including a hydrocarbon precursor, and generating a plasma using adual radio frequency (RF) source by pulsing low frequency (LF) power.Pulsing the LF power at a high power, high frequency, and low duty cycle(DC) may increase the modulus, and thus the selectivity, of the AHMfilm. A carrier gas of substantially helium may also reduce sputteringof the AHM film.

In one aspect of the embodiments herein, a method of forming an ashablehard mask (AHM) film is provided, the method may include exposing asemiconductor substrate to a process gas may include a hydrocarbonprecursor gas and helium gas, substantially without any other inert gas;and depositing on the substrate an AHM film by a plasma enhancedchemical vapor deposition (PECVD) process, wherein the process mayinclude igniting a plasma generated by a dual radio frequency (RF)plasma source including a high frequency (HF) component and a lowfrequency (LF) component; the HF power is constant during deposition,and the LF power is pulsed, with at least about 3000 W per 300 mm waferand a duty cycle between about 10% and about 75%.

In some embodiments, the hydrocarbon precursor gas may include compoundshaving a molecular weight of at most about 50 g/mol. In someimplementations, the hydrocarbon precursor gas may include compoundshaving a C:H ratio of at least 0.5. In various implementations, thehydrocarbon precursor gas may include acetylene (C₂H₂). In someembodiments, the hydrocarbon precursor has a partial pressure betweenabout 1-2% of the process gas.

In various embodiments, the LF power is provided at a frequency of lessthan or equal to about 2 MHz. In various embodiments, the LF power isbetween about 3500 W and about 6500 W per 300 mm wafer. In someimplementations, the LF power is pulsed at a frequency of at least about100 Hz. In some implementations, the LF power is pulsed at a frequencybetween about 100 Hz and about 1000 Hz.

In some embodiments, the LF power duty cycle is between about 10% andabout 50%. In various embodiments, the LF power duty cycle is betweenabout 60% and about 90%. In various implementations, the LF power has anon period for a duration of between about 200 microseconds and about 300microseconds. In some embodiments, the method is performed in amulti-station reactor.

In various implementations, the internal stress of the AHM film is atmost about −1400 MPa. In various embodiments, the modulus of the AHMfilm is at least about 80 GPa. In some embodiments, the density of theAHM film is at least about 1.5 g/cm³.

In some implementations, the hydrogen concentration of the AHM film isat most about 25 atomic percent. In various embodiments, the thicknessof the AHM film is at most about 2500 nm. In some embodiments, a gapbetween the pedestal and the showerhead is less than about 20 mm.

In some embodiments, the method may further include patterning thedeposited AHM film and etching the patterned AHM film to define featuresof the AHM film in the substrate. In various embodiments, the method mayfurther include etching layers in the substrate underlying the AHM film.

In another aspect of the embodiments herein, a method of forming anashable hard mask (AHM) film is provided, the method including: exposinga semiconductor substrate to a process gas may include a hydrocarbonprecursor gas and an inert gas; and depositing on the substrate an AHMfilm by a plasma enhanced chemical vapor deposition (PECVD) process,wherein the process may include: igniting a plasma generated by a dualradio frequency (RF) plasma source including a high frequency (HF)component and a low frequency (LF) component; the HF power is constantduring deposition, and the LF power is pulsed, with at least about 3000W per 300 mm wafer and the LF power on time per duty cycle is less than300 microseconds.

In some implementations, the LF power duty cycle is between about 10%and 50%. In various embodiments, the LF power on time is between 200microseconds and 300 microseconds. In some implementations, the LF poweris pulsed at a frequency of at least 100 Hz.

These and other features will be described in more detail below withreference to the figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a process flow diagram showing relevant operations of methodsof using ashable hard masks in etching operations according to variousembodiments.

FIGS. 2A and 2B are illustrations of line-bending of a patterned ashablehard mask.

FIG. 3 is a process flow diagram showing relevant operations of methodsof forming ashable hard masks by modulating dual radio frequency plasmagenerators according to various embodiments.

FIG. 4A-C are illustrations of various properties that relate to pulsinglow frequency (LF) power.

FIG. 5 shows a graph of refractive index of an ashable hard mask as afunction of LF power for various embodiments.

FIG. 6 shows a graph of refractive index of an ashable hard mask as afunction of stress for various embodiments.

FIG. 7 shows a schematic illustration of a plasma enhanced chemicalvapor deposition (PECVD) chamber suitable for practicing variousembodiments.

FIG. 8 shows another schematic illustration of another plasma enhancedchemical vapor deposition (PECVD) chamber suitable for practicingvarious embodiments.

FIG. 9 shows a schematic illustration of a module cluster suitable forpracticing various embodiments.

DETAILED DESCRIPTION

Introduction and Context

In semiconductor processing, masking methods are used to pattern andetch substrates. As substrate aspect ratios increase, the demand forhighly selective hard masks increases. Masks that have high etchselectivity and yet are easy to remove without damage to the substrateare important to processing substrates. Ashable hard masks (AHMs) can beused as masks in etch stop layers or during selective etching, or wherea photoresist may not be thick enough to mask the underlying layer. AHMsmay also be used on glass substrates used for displays and othertechnologies.

AHM films have a chemical composition that allows them to be removed bya technique referred to as “ashing,” “plasma ashing,” or “dry stripping”once they have served their purpose. One example of an AHM film is anamorphous carbon layer or film. An AHM film is generally composed ofcarbon and hydrogen with, optionally, a trace amount of one or moredopants (e.g., nitrogen, fluorine, boron, and silicon). The bondingstructure of an AHM can vary from sp² (graphite-like) or sp³(diamond-like), or a combination of both, depending on the depositionconditions.

FIG. 1 is a process flow diagram showing relevant operations of methodsof using an AHM as a hard mask in etching operations. While thedescription below refers chiefly to semiconductor substrates, themethods may also be applied to layers on other types of substratesincluding glass substrates. Examples of materials that may be maskedwith the AHM include dielectric materials such as oxides (e.g., SiO₂)and nitrides (e.g., SiN and TiN), polysilicon (Poly-Si), and metals suchas aluminum (Al), copper (Cu), and tungsten (W). In certain embodiments,the AHMs described herein are used to pattern oxides, nitrides, orpolysilicon layers.

In operation 102, an ashable hard mask is deposited on the layer to beetched by plasma enhanced chemical vapor deposition (PECVD). PECVDprocesses involve generating plasma in the deposition chamber. Asdescribed further below with reference to FIG. 2, a dual radio frequency(RF) plasma sources that include a high frequency (HF) power and a lowfrequency (LF) power may be used. In some processes, one or more AHMlayers are deposited.

In operation 106, a photoresist layer is deposited, exposed, anddeveloped in accordance with the desired etch pattern. In someimplementations, an anti-reflective layer (ARL) may be deposited on theAHM film prior to photoresist deposition.

In operation 108, the AHM film is opened by etching the exposed portionsof the AHM. Opening the AHM may be performed by a fluorine-rich dryetch.

Next, in operation 110, the substrate layer is selectively etched totransfer the pattern to the substrate layer. The selective etch may beperformed such that the substrate layer is etch without substantiallydiminishing the AHM walls. Examples of etches can include radical and/orionic-based etches. Examples of etch chemistries can includehalogen-based etch chemistries such as fluorine-containing andchlorine-containing etch chemistries. For example, capacitively-coupledplasmas generated from fluorocarbon-containing process gases may be usedto selectively etch oxide layers. Specific examples of process gasesinclude C_(x)F_(y)-containing process gases, optionally with oxygen (O₂)and an inert gas, such as C₄Hg/CH₂F₂/O₂/Ar.

Lastly, in operation 112, a technique referred to as ashing, plasmaashing, or dry stripping is used to remove the AHM. Ashing may beperformed by an oxygen-rich dry etch. Often, oxygen is introduced in achamber under vacuum and RF power creates oxygen radicals in plasma toreact with the AHM and oxidize it to water (H₂O), carbon monoxide (CO),and carbon dioxide (CO₂). Optionally, any remaining AHM residue may alsobe removed by wet or dry etching processes after ashing. The result is apatterned substrate layer.

High aspect ratio patterning uses AHMs having high etch selectivity.Etch selectivity can be determined by comparing the etch rate of the AHMlayer to an underlying layer. The etch selectivity can sometimes beapproximated by determining the hydrogen content, refractive index (RI),density, and modulus, or rigidity, of the AHM layer. Typically, lowerhydrogen content, lower RI, higher density, and higher modulus, or amore rigid, AHM is able to withstand higher etch rates in an etchprocess involving more ion bombardment. Therefore, AHMs with lowerhydrogen content, lower RE, higher density, and/or higher modulus havehigher selectivity and lower etching rate and can be used moreefficiently and effectively for processing high aspect ratiosemiconductor processes. The desired etch selectivity of the AHM maydepend on the etching process and the composition of the underlyinglayers, but the correlation between etch selectivity and the materialproperties above remains the same regardless of the etching process orcomposition of the underlying layers. The selectivity correlations asdescribed here applies to all types of underlying layers, includingpolysilicon layers, oxide layers, and nitride layers.

It has been observed that AHM films produced using continuous wave (CW)LF and HF plasma may have certain problems. For example, they may haverelatively high internal stress, high hydrogen content, low density,and/or low hardness/modulus. The ever-shrinking feature size ofnext-generation memory and logic applications requires films that do notexhibit a significant amount of line-bending, or the distortion offeatures after the pattern has been etched into a stack of films. FIGS.2A-B are illustrations of line-bending of a resist. FIG. 2A shows afeature 200 of a patterned AUM having a height, or thickness, ‘h’ and aline width ‘w’. FIG. 2A has no line bending, which is the idealcondition for features of an AHM. FIG. 2B shows the same feature butwith significant line-bending, which may have a vertical aspect 223 anda horizontal aspect 225. As illustrated, line-bending may be manifest asa curved, angled, or otherwise bent horizontal component. In some cases,line-bending is manifest as vertical component that deviates fromperpendicular (normal) to a plane of substrate on which the line isformed. In the depicted embodiment, the line has a fan-like shape.Line-bending is undesirable for various reasons, among which are that itincreases the line edge roughness (LER) and line width roughness (LWR)and reduces the critical dimension uniformity (CDU) of the AHM andunderlying layers etched using the AHM. In general, line bending maycause distortion of features after the pattern has been etched into astack of films.

Line-bending of an AHM can be roughly modeled by the following equation:

${{Line}\mspace{14mu}{bending}\mspace{20mu}{propensity}} \propto {\frac{\sigma}{E}\left( \frac{h}{w} \right)^{2}}$

Where σ and E are the internal compressive stress and modulus of theAHM, respectively. This equation demonstrates that line-bending isdirectly related to stress and height, increasing with higher stress orheight, (i.e. thickness), while inversely related to modulus and width,decreasing with increased modulus or width. As features size shrinks,the width of AHM features decrease to meet new critical dimensionrequirements. Furthermore, the required thickness of the AHM for an etchprocess is inversely proportional to its selectivity; higher selectivityallows for a thinner AHM, and lower selectivity requires a thicker AHM.Thus, line-bending may be reduced by reducing the stress, increasing themodulus, or reducing the thickness, but reducing the thickness requiresincreasing selectivity.

Highly selective AHM films typically have high stress levels. Somemethods to form AHMs use continuous wave RF power plasma in a PECVDprocess. Using continuous wave RF power results in continuous ionbombardment, which increases film density, thereby increasing etchselectivity by creating more sp³ bonds between carbon atoms. However,continuous ion bombardment may also incorporate excessive unboundhydrogen atoms in the film and modify the growing film by bombardmentwith heavy atomic weight ions. These effects may increase the stress ofthe deposited AHM film, which limits AHM applications because highstress AHMs are more likely to exhibit line-bending.

On the other hand, AHMs with low stress levels, and concomitant lessline bending, have lower selectivity. Some methods to form AHMs pulse RFpower plasma during a PECVD process. Pulsing the RF power results inpulsed ion bombardment, which decreases stress levels, thereby reducingline-bending. However, pulsed ion bombardment may also reduce the numberof sp³ bonds, which leads to lower density and lower selectivity. Thelower selectivity requires a thicker AHM for the same etch process,which increases the amount of line-bending.

According to various embodiments, methods of forming AHM films producefilms that have high selectivity and low stress. An AHM film depositiontechnique uses low frequency (LF) RF pulsing, with or without continuouswave (CW) high frequency (HF) RF, at high single station LF power toreduce the internal stress (make the stress more neutral), reduce thehydrogen content, and increase the selectivity of the diamond-likecarbon (DLC) films usable as AHMs. These methods yield AHMs withimproved selectivity at a given stress level, or a decreased stresslevel at a given selectivity, thus improving the AHM performance insemiconductor processing.

In various embodiments, an AHM deposition technique uses low frequency(LF) RF pulsing, with or without continuous wave (CW) high frequency(HF) RF, at high single station LF power to reduce the internal stress(make the stress more neutral), reduce the hydrogen content, andincrease the selectivity of the diamond-like carbon (DLC) films whenused as an ashable hard mask (AHM). There may be three main componentsto this process. First, high LF power may be used at each station. Invarious embodiments, the general range of the process is 3500 to 6500 Wof LF power per station with a significant stress reduction anddensification of the DLC film. Second, a carrier gas that containssubstantially only helium is used. Argon is conventionally used to helpcontain plasma for the sake of uniformity. However, Argon ions maysputter the AHM at high ion energies, reducing the density andselectivity. Third, fast pulsing frequency and low duty cycle, resultingin a short LF “on time” allows the plasma to increase the peak ionenergy while maintaining a low mean ion density. In other words, becauseof the fast LF pulsing, there are fewer ions with higher energy thancontinuous wave plasma. The benefits of high LF power may be mostsignificant when pulsing is employed.

Certain embodiments use relatively fast (greater than 100 Hz at 25% dutycycle) LF pulsing, with or without CW HF, at high LF power per stationin a He/hydrocarbon precursor only atmosphere.

FIG. 3 shows a process flow diagram showing relevant operations ofmethods of forming AHMs by modulating dual RF plasma power according tovarious embodiments. In operation 302 a substrate is received in aprocess chamber. The substrate may be provided to the chamber in thisoperation, or the substrate may already be in the chamber from a prioroperation. In operation 304 the substrate is exposed to a process gasincluding a hydrocarbon precursor. In addition to hydrocarbonprecursors, an inert gas carrier may be used. The inert gas may includehelium (He), argon (Ar), nitrogen (N₂), hydrogen (H₂), or a combinationof any of these. In some embodiments the inert gas is substantiallyentirely helium.

Next, in operation 306, an ashable hard mask is deposited on thesubstrate by a PECVD process by igniting plasma using a dual RF plasmasource to produce a plasma having a pulsed low frequency (LF) componentand a high frequency (HF) component. The pulsed LF component may beproduced by pulsing a LF power source. In some embodiments, pulsing theLF RF power includes using a high power, fast pulse, and low duty cycleto generate a high peak energy ion bombardment with a low mean iondensity.

The result of operation 306 is an AHM film. This process produces a filmwith better density to stress ratio and higher selectivity. Depending onthe duty cycle of the LF power, the pulsing frequency may be adjusted tomaintain the high mean ion energy, while altering the mean ion density.In some embodiments the DC may be decreased to produce a low modulus,low stress, film. In other embodiments, DC may be increased to produce ahigh modulus, high stress, film. Increasing DC may also increase thedeposition rate of the AHM film. Both types of films may be desirabledepending on other process conditions.

Proposed Mechanism

FIGS. 4A-C demonstrate how LF power is pulsed, and how that may improvethe deposition results of an AHM deposition. FIG. 4A shows pulsed LFpower over time, and the associated duty cycle. At times 402 the LFpower is on, or set at high power, while at times 404 the LF power isoff, or set at low power. As illustrated and known in the art, a dutycycle is defined by the equation DC=t_(on)/(t_(on)+t_(off)), andrepresents the percentage of time that the power is on, or set at highpower. Duty cycle and pulse frequency together can be used to determinethe time that LF power is on, i.e. a 100 Hz pulse frequency with a dutycycle of 25% indicates that the LF power is on for 2.5 ms, and off for7.5 ms.

FIG. 4B is an illustration of a surface of the substrate duringdeposition of an AHM when the LF power is on and off according to apossible mechanism for forming AHM films in accordance with thisdisclosure. State 410 illustrates the substrate surface when the LFpower is on. LF power generally energizes the ion component of plasma,and when the LF power is on carbon ions 412 bombard the surface of thesubstrate. Ion bombardment may increase density, as discussed above, butthe higher density of charged ions may also increase the stress of theAHM, which is undesirable, and may also form a charged surface 414.State 420 illustrates a possible condition of the substrate surface whenthe LF power is off. When the LF power is off, the ion bombardment stopsor is substantially reduced, and the ions embedded into the substratesurface absorb electrons 422 to develop a neutral charge. While notwishing to be bound by theory, this allows the ions to form a moreordered structure 424, reducing the stress within the substrate surface,which is desirable. However, this reduction in stress may come at theexpense of reduced density, and thus selectivity. By pulsing the LFpower, the surface may alternate between states 410 and 420 to depositan AHM having a reduced internal stress.

FIG. 4C is a graph of plasma temperature over time, where temperature isin electron volts. When LF power is pulsed, there is a brief high ionenergy peak 442 upon ignition, followed by an energy shelf 444 where thetemperature stabilizes, and finally a low temperature region 446 whenthe LF power is turned off. The energy peak 442 has a substantiallystatic time duration, i.e. regardless of how fast the LF power ispulsed, the energy peak will last for substantially the same amount oftime. The energy shelf 444, on the other hand, exists for more or lesstime depending on how long the LF power is on. Thus, at high pulsefrequencies and low duty cycles, the LF power exhibits a higher mean ionenergy while maintaining a low mean ion density. Within a certain rangeof energy, higher mean ion energy increases the modulus of the hardmask,which is desirable, while low mean ion density decreases stress, whichis also desirable.

In some embodiments the duty cycle may be increased to increase the meanion density, which may result in a denser, higher modulus AHM, at theexpense of additional stress. AHM films deposited using a higher DC maystill have a higher mean ion energy by using techniques disclosedherein, resulting in a film with better selectivity than other filmswith the same amount of internal stress.

The plasma also comprises the inert gas, which in some embodiments theinert gas is helium substantially without any other gas. Heavier inertgases, such as Argon, are commonly used to help contain plasma for thesake of uniformity, however, such ions may sputter the AHM at ionenergies above 3000 W. This is obviously undesirable for a depositionprocess. Helium may be used without sputtering the AHM, at low ionenergies, which is desirable and results in a more uniform deposition.

Process Window

This section describes various process parameters that may be employedto produce AHM films. The process parameters are provided for a plasmaenhanced chemical vapor deposition process that takes place in a processchamber such as one described below.

In various embodiments, the total pressure in the process chamber isbetween about 0.5 Torr and about 20 Torr. In some embodiments, pressureis between about 5 Torr and about 10 Torr, or between about 0.5 Torr andabout 1.5 Torr. In some embodiments, the hydrocarbon precursor ispresent in the process chamber at a relatively low partial pressure,e.g., between about 0.01 Torr and about 4 Torr, as discussed in U.S.Pat. Nos. 7,981,777 and 7,981,810, which are incorporated by referenceherein in their entireties. In certain embodiments, the hydrocarbonprecursor partial pressure is at or below about 0.2 Torr.

In some embodiments, the hydrocarbon precursor is one defined by theformula C_(x)H_(y), wherein X is an integer between 2 and 10, and Y isan integer between 2 and 24. Examples include methane (CH₄), acetylene(C₂H₂), ethylene (C₂H₄), propylene (C₃H₆), butane (C₄H₁₀), cyclohexane(C₆H₁₂), benzene (C₆H₆), and toluene (C₇H₈). In certain embodiments thehydrocarbon precursor is a halogenated hydrocarbon, where one or morehydrogen atoms are replaced by a halogen, particularly fluorine,chlorine, bromine, and/or iodine. In some embodiments the hydrocarbonprecursor comprises compounds having a molecular weight of at most about50 g/mol. In some embodiments the hydrocarbon precursor has a ratio ofC:H of at least 1:2. In some embodiments the hydrocarbon precursor isacetylene (C₂H₂). In some embodiments, two or more hydrocarbonprecursors may be used.

In some embodiments the inert gas comprises at least about 50% or atleast about 80% or at least about 95% helium by volume of all inert gasused. In some embodiments the inert gas is helium substantially withoutany other inert gas.

Precursor gas volumetric flow rates depend on the particular processchamber, substrate, and other process conditions. Examples of volumetricflow rates that may be used for a single 300 mm substrates are betweenabout 10 sccm and about 1,000 sccm of acetylene and between about 250sccm and about 5,000 sccm of helium. In some embodiments the flow rateof acetylene is between about 1% and about 3% of the total flow rate andhelium comprises the rest of the total flow rate. In some embodimentsthe volumetric flow is between about 15 sccm and about 45 sccm C₂H₂, andbetween about 1455 sccm and about 1485 sccm helium. In some embodimentsthe volumetric flow is between about 18 sccm and about 20 sccm C₂H₂, andbetween about 1480 sccm and about 1482 sccm helium, all values per 300mm substrate. In some embodiments the volumetric flow rate is betweenabout 40 sccm and about 45 sccm C₂H₂, and between about 1455 sccm andabout 1460 sccm helium. Unless otherwise specified, the flow ratesdisclosed herein are for a single station tool configured for 300 mmwafers. Flow rates generally scale linearly with the number of stationsand substrate area.

The AHM film deposition methods described herein may be performed at anyappropriate process temperature to obtain desired AHM characteristics,with examples ranging from about 50° C. to about 550° C. In someembodiments the process temperature is between about 100° C. and about200° C. In some embodiments the process temperature is between about150° C. and about 175° C. Process temperature can affect the stress,selectivity, and transparency at least in part due to sp² bond versussp³ bond formation. Higher temperatures favor sp² rich amorphous carbonnetwork formation as the high temperatures enable easy breakage of C—Hbonds and subsequent diffusion of hydrogen. For example, films depositedat temperatures above about 500° C. may have significantly more sp² CHand CH₂ bonds and relatively fewer sp³ bonds, which have increasedcarbon content and higher density, and correlate with increased etchselectivity. However, these sp²-rich films may not be suitable for thickhard mask applications. For example, at 2,000 Å and above, the films maynot be transparent enough for mask alignment. 633 nm lasers may be usedfor transparent films and semi-transparent films but not for more opaquefilms such as produced at high temperatures. U.S. Pat. No. 7,981,810,previously incorporated herein by reference in its entirety, providesprocess conditions for deposition of selective and transparent AHM's atlower temperatures and/or with dilute hydrocarbon precursor flows. AHMfilms deposited at lower temperatures, e.g., below about 400° C. mayhave more less sp² bonding compared to films deposited at highertemperatures.

In some embodiments, low frequency (LF) RF power refers to an RF powerhaving a frequency between about 100 kHz and about 2 MHz. In someembodiments, pulsing frequency may be limited by the operationcapability of the LF generator. In some embodiments, LF RF power has anRF power with a frequency of about 400 kHz, for example 430 kHz. Highfrequency RF power refers to an RF power having a frequency betweenabout 2 MHz and about 60 MHz. In some embodiments, HF RF power has an RFpower with a frequency of about 13.56 MHz.

In some embodiments, HF and LF RF components can be pulsed in asynchronized manner. If an HF component is pulsed, it is pulsed fromhigh to low power and not turned off to avoid plasma sheath collapse. Insome embodiments, pulsing only LF RF power may be advantageous to formmore stable plasma.

In some embodiments, the LF power is pulsed while HF power is constant.In various embodiments, the LF power is pulsed by switching the LF poweron and off. In some embodiments, the LF ‘on’ power is at least 3000 Wper 300 mm substrate. In some embodiments the LF on power is betweenabout 3500 W and about 6500 W per 300 mm substrate. In some embodiments,the LF ‘off’ power is OW. In various embodiments, the LF power is pulsedby switching the LF between non-zero power levels, such that the LF offpower is between OW and the LF on power. In some embodiments, the LFpower is pulsed between about 1000 W and about 6000 W. In someembodiments, the HF power per substrate ranges is about OW and about 150W per 300 mm substrate. In some embodiments, the HF power per substrateranges between about OW and about 800 W. In many embodiments, theminimum power of the HF RF component and the minimum power of the LF RFcomponent are sufficient to maintain a plasma. All powers providedherein are per 300 mm substrate. RF power as described herein generallyscales linearly with number of stations and area of wafers. The powervalues may be represented on a per area basis, e.g., 2500 W may also berepresented as 0.884 W/cm².

Duty cycle (DC) for LF pulsing may range from about 10% to about 90%. Insome embodiments the DC is between about 10% and about 50%, betweenabout 10% and about 30%, or between about 10% and about 20%. In someembodiments the DC is between about 60% and about 90%, between about 60%and about 90%, or between about 60% and about 75%. In variousembodiments, the LF power is pulsed at a frequency of between about 100Hz and about 1000 Hz. In some embodiments, the LF power is pulsed at afrequency of at least about 200 Hz, or at least about 300 Hz. In someembodiments the DC and pulse frequency are set so that the LF power ontime duration is between about 200 μs and about 2500 μs and the LF poweroff time duration is between about 800 μs and about 7500 μs. In someembodiments the LF power has an on period for a duration between about200 μs and about 300 μs.

In some embodiments the gap between the pedestal and the showerhead isless than about 0.75 inches (20 mm) or between about 0.25 inches (about6 mm) and about 0.75 inches (about 20 mm). As the RF power of the plasmaincreases, the gap between the pedestal and the showerhead may beincreased without reducing the quality of the deposited AHM.

In some processes herein the AHM film deposits at a rate of at least 700Å/min. In some embodiments the AHM film deposits at a rate of betweenabout 700 Å/min and about 900 Å/min. The deposition rate of the AHM filmmay depend on the DC, as a longer mean ‘on’ time for the LF power willincrease the deposition rate.

In some embodiments, the process conditions for depositing an AHM filminclude pulsing the LF power with at least about 3000 W per 300 mmwafer, with a duty cycle between about 10% and about 75%, and an inertgas that is substantially helium. In some embodiments, the processconditions include pulsing the LF power with at least 6000 W per 300 mmwafer, with a duty cycle between 10% and 75%, and an inert gas that issubstantially helium. In some embodiments, the process conditionsinclude pulsing the LF power with at least about 3000 W per 300 mmwafer, with a duty cycle between 10% and 40%, and an inert gas that issubstantially helium.

Film Properties

AHM films produced in accordance with the disclosed methods aretypically composed primarily of carbon and hydrogen, but other elementsmay be present in the film. Generally, the lower the atomic percent ofhydrogen in the mask, the higher the modulus and selectivity. In someembodiments other elements may be added to the gas mixture, for example,if a halogenated hydrocarbon is used, the halogen may comprise apercentage of the film composition. In some embodiments, the hydrogenconcentration is at most about 25 percent atomic. In some embodiments,the hydrogen concentration is between about 24 and 25 percent atomic. Insome embodiments the carbon concentration is at least about 70 percentatomic. In some embodiments the carbon concentration is between about 70and 76 percent atomic. Examples of other elements that may be present inthe AHM film include halogens, Nitrogen, sulfur, boron, oxygen,tungsten, titanium, and aluminum. Typically, such other elements arepresent in amounts not greater than about 10 percent atomic.

In some embodiments, an AHM film produced in accordance with the methodsdescribe herein has an internal stress magnitude of at most about −1400MPa, or between about −200 MPa and about −1400 MPa. (negative internalstress denotes a compressive stress, such that lower values have lessinternal stress) In some embodiments, the AHM film has an elasticmodulus of at least about 80 GPa, or between about 145 GPa and 160 GPa.In some embodiments, the AHM film has a hardness of at least about 9GPa, or between about 15 GPa and about 17 GPa. In some embodiments, theAHM film has a density of at least about 1.5 g/cm³, or between about 1.8g/cm³ and about 1.9 gm/cm³.

In some embodiments an AHM film produced in accordance with the methodsdescribed herein has an extinction coefficient at 633 nm of at mostabout 0.4. The extinction coefficient may correlate with the ability oflight to move through the AHM film, or the transparency of the film. Insome embodiments, AHM films are transparent or translucent. AHM filmswithout sufficiently low values of extinction coefficient may requireadditional operations in a later etch process to etch the AHM film,which is undesirable.

In some embodiments the thickness of an AHM film deposited in accordancewith methods disclosed herein is between about 100 nm and about 2500 nm.Generally, the desired thickness of an AHM film may vary depending onthe thickness of the underlying layers to be etched and the etchselectivity of the AHM, with thicker underlying layers to be etchedrequiring a thicker AHM. As discussed above, AHM films are used to etcha variety of underlying materials, and may have a different etchselectivity for each material. Etch selectivity of an AHM can berepresented as a ratio of the etch rate of a material and the etch rateof the AHM, and may vary for different materials and etch chemistries.

Applications

AHMs are typically used for creating features of semiconductor devicesby etching one or more underlying layers of a substrate. Materials thatmay be etched using an AHM may include silicon (single crystal,polysilicon, or amorphous silicon), silicon oxide, silicon nitride, andtungsten. In some embodiments multiple layers are stacked and etchedusing a single AHM. Examples of such stacks include a layer of siliconand a layer of silicon oxide, and a layer of tungsten and a layer ofsilicon nitride. In some embodiments a stack includes repeating layersthat are etched using a single AHM. Examples of such repeating layersinclude repeating layers of silicon oxide/polysilicon (OPOP). Front endof line and back end of line features may be etched using an AHM asdisclosed herein. Memory or logic device features may be patterned.Examples of memory devices include: DRAM, NAND, and 3D NAND.

Examples

FIGS. 5 and 6 illustrate the effect of LF power when under pulsing orcontinuous wave conditions on refractive index of an AHM. Refractiveindex, or RI, can generally be used as a proxy for the selectivity ofthe material, with higher refractive index indicating higher selectivityof an AHM. Continuous wave power is where the LF power is heldrelatively constant during deposition.

FIG. 5 is a graph of refractive index as a function of LF power. Line504 represents measurements from AHM deposited using a continuous wave(CW) LF power, while Line 502 represents measurements from AHM depositedby pulsing LF power as described herein. FIG. 5 illustrates that aspower is increased, the refractive index, and thus selectivity, of anAHM deposited using a continuous wave technique decreases. In contrast,as the power of pulsed LF power increases, the refractive index, orselectivity, of an AHM increases. Thus, as LF power increases, acontinuous wave technique will result in a lower selectivity AHM, whilea pulse technique will result in a higher selectivity AHM.

FIG. 6 is a graph of refractive index as a function of internal stress,where negative stress is a compressive stress, and a more neutral stressis desirable. Line 606 is a line of refractive index as a function ofstress for some AHM, illustrating that as refractive index, orselectivity, is increased, internal stress generally increases. Line 604illustrates that, for continuous wave power, as LF power increases, therefractive index decreases, while the internal compressive stressincreases. Both are undesirable, indicating that a lower LF power isdesirable for a continuous wave technique. In contrast, line 602illustrates that as LF power increases for pulsed LF power, therefractive index and the stress increase. Line 602, however, is steeperthan line 606, indicating that as pulsed LF power is increased, therefractive index increases at a higher rate than the internal stressthan line 606. Thus, while increasing LF power increases stress, theincrease in stress is offset by a greater than normal increase inselectivity.

The table below presents a variety of film properties for two differentfilms deposited according to some embodiments disclosed herein. The 3625W process deposited an AHM film by pulsing LF power between OW and 3625W while exposing a substrate to a process gas of 44 sccm of C₂H₂ and1466 sccm of helium. The 6000 W process deposited an AHM film by pulsingLF power between OW and 6000 W while exposing a substrate to a processgas of 18 sccm of C₂H₂ and 1482 sccm of helium. Range % NU is ameasurement of the non-uniformity of the deposition. H % is the percentof hydrogen in the AHM, as measured using hydrogen forward scattering.XRR density is the density as measured by x-ray reflectivity.

Dep Rate RI @ Stress Range Hardness Modulus H % XRR Density Process(Å/min) 633 nm (MPa) % NU (MPa) (MPa) (HFS) (g/cm³) 3625 W 872.2 2.307−632.0 3.6 15.6 145.3 25% 1.88 6000 W 764.0 2.334 −695.8 3.3 16.5 152.024% 1.90

Apparatus

Embodiments can be implemented in a plasma enhanced chemical vapordeposition (PECVD) reactor. Such a reactor may take many differentforms. Various embodiments are compatible with existing semiconductorprocessing equipment—in particular, PECVD reactors such as Sequel™ orVector™ reactor chambers available from Lam Research Corporation. Thevarious embodiments may be implemented on a multi-station or singlestation tool. In specific embodiments, the 300 mm Lam Vector™ toolhaving a 4-station deposition scheme or the 200 mm Sequel™ tool having a6-station deposition scheme are used.

Generally, the apparatus will include one or more chambers or reactorsthat each include one or more stations. Chambers will house one or morewafers and are suitable for wafer processing. The one or more chambersmaintain the wafer in a defined position or positions, by preventingrotation, vibration, or other agitation. In some embodiment, a waferundergoing AHM deposition is transferred from one station to anotherwithin a chamber during the process. For example, a 2000 Å AHMdeposition may occur entirely at one station, or 500 Å of film may bedeposited at each of four stations in accordance with variousembodiments. Alternatively, any other fraction of the total filmthickness may be deposited at any number of stations. In variousembodiments where more than one AHM is deposited, more than one stationmay be used to deposit each AHM layer. During processing, each wafer isheld in place by a pedestal, wafer chuck, and/or other wafer holdingapparatus. For certain operations where the wafer is to be heated, theapparatus may include a heater such as a heating plate.

FIG. 7 schematically shows an embodiment of a process station 700 thatmay be used to deposit material using plasma enhanced chemical vapordeposition (PECVD). For simplicity, the process station 700 is depictedas a standalone process station having a process chamber body 702 formaintaining a low-pressure environment. However, it will be appreciatedthat a plurality of process stations 700 may be included in a commonprocess tool environment. Further, it will be appreciated that, in someembodiments, one or more hardware parameters of process station 700,including those discussed in detail below, may be adjustedprogrammatically by one or more computer controllers.

Process station 700 fluidly communicates with reactant delivery system701 for delivering process gases to a distribution showerhead 706.Reactant delivery system 701 includes a mixing vessel 704 for blendingand/or conditioning process gases for delivery to showerhead 706. One ormore mixing vessel inlet valves 720 may control introduction of processgases to mixing vessel 704. Similarly, a showerhead inlet valve 705 maycontrol introduction of process gasses to the showerhead 706.

For example, the embodiment of FIG. 7 includes a vaporization point 703for vaporizing liquid reactant to be supplied to mixing vessel 704. Insome embodiments, vaporization point 703 may be a heated vaporizer. Thereactant vapor produced from such vaporizers may condense in downstreamdelivery piping. Exposure of incompatible gases to the condensedreactant may create small particles. These small particles may clogpiping, impede valve operation, contaminate substrates, etc. Someapproaches to addressing these issues involve sweeping and/or evacuatingthe delivery piping to remove residual reactant. However, sweeping thedelivery piping may increase process station cycle time, degradingprocess station throughput. Thus, in some embodiments, delivery pipingdownstream of vaporization point 703 may be heat traced. In someexamples, mixing vessel 704 may also be heat traced. In one non-limitingexample, piping downstream of vaporization point 703 has an increasingtemperature profile extending from approximately 100° C. toapproximately 150° C. at mixing vessel 704.

In some embodiments, reactant liquid may be vaporized at a liquidinjector. For example, a liquid injector may inject pulses of a liquidreactant into a carrier gas stream upstream of the mixing vessel. In onescenario, a liquid injector may vaporize reactant by flashing the liquidfrom a higher pressure to a lower pressure. In another scenario, aliquid injector may atomize the liquid into dispersed microdroplets thatare subsequently vaporized in a heated delivery pipe. It will beappreciated that smaller droplets may vaporize faster than largerdroplets, reducing a delay between liquid injection and completevaporization. Faster vaporization may reduce a length of pipingdownstream from vaporization point 703. In one scenario, a liquidinjector may be mounted directly to mixing vessel 704. In anotherscenario, a liquid injector may be mounted directly to showerhead 706.

In some embodiments, a liquid flow controller upstream of vaporizationpoint 703 may be provided for controlling a mass flow of liquid forvaporization and delivery to process station 700. For example, theliquid flow controller (LFC) may include a thermal mass flow meter (MFM)located downstream of the LFC. A plunger valve of the LFC may then beadjusted responsive to feedback control signals provided by aproportional-integral-derivative (PID) controller in electricalcommunication with the MFM. However, it may take one second or more tostabilize liquid flow using feedback control. This may extend a time fordosing a liquid reactant. Thus, in some embodiments, the LFC may bedynamically switched between a feedback control mode and a directcontrol mode. In some embodiments, the LFC may be dynamically switchedfrom a feedback control mode to a direct control mode by disabling asense tube of the LFC and the PID controller.

Showerhead 706 distributes process gases toward substrate 712. In theembodiment shown in FIG. 7, substrate 712 is located beneath showerhead706, and is shown resting on a pedestal 708. It will be appreciated thatshowerhead 706 may have any suitable shape, and may have any suitablenumber and arrangement of ports for distributing processes gases tosubstrate 712.

In some embodiments, a microvolume 707 is located beneath showerhead706. Performing an ALD and/or CVD process in a microvolume rather thanin the entire volume of a process station may reduce reactant exposureand sweep times, may reduce times for altering process conditions (e.g.,pressure, temperature, etc.), may limit an exposure of process stationrobotics to process gases, etc. Example microvolume sizes include, butare not limited to, volumes between 0.1 liter and 2 liters. Thismicrovolume also impacts productivity throughput. While deposition rateper cycle drops, the cycle time also simultaneously reduces. In certaincases, the effect of the latter is dramatic enough to improve overallthroughput of the module for a given target thickness of film.

In some embodiments, pedestal 708 may be raised or lowered to exposesubstrate 712 to microvolume 707 and/or to vary a volume of microvolume707. For example, in a substrate transfer phase, pedestal 708 may belowered to allow substrate 712 to be loaded onto pedestal 708. During adeposition process phase, pedestal 708 may be raised to positionsubstrate 712 within microvolume 707. In some embodiments, microvolume707 may completely enclose substrate 712 as well as a portion ofpedestal 708 to create a region of high flow impedance during adeposition process.

Optionally, pedestal 708 may be lowered and/or raised during portionsthe deposition process to modulate process pressure, reactantconcentration, etc., within microvolume 707. In one scenario whereprocess chamber body 702 remains at a base pressure during thedeposition process, lowering pedestal 708 may allow microvolume 707 tobe evacuated. Example ratios of microvolume to process chamber volumeinclude, but are not limited to, volume ratios between 1:700 and 1:10.It will be appreciated that, in some embodiments, pedestal height may beadjusted programmatically by a suitable computer controller.

In another scenario, adjusting a height of pedestal 708 may allow aplasma density to be varied during plasma activation and/or treatmentcycles included in the deposition process. At the conclusion of thedeposition process phase, pedestal 708 may be lowered during anothersubstrate transfer phase to allow removal of substrate 712 from pedestal708.

While the example microvolume variations described herein refer to aheight-adjustable pedestal, it will be appreciated that, in someembodiments, a position of showerhead 706 may be adjusted relative topedestal 708 to vary a volume of microvolume 707. Further, it will beappreciated that a vertical position of pedestal 708 and/or showerhead706 may be varied by any suitable mechanism within the scope of thepresent disclosure. In some embodiments, pedestal 708 may include arotational axis for rotating an orientation of substrate 712. It will beappreciated that, in some embodiments, one or more of these exampleadjustments may be performed programmatically by one or more suitablecomputer controllers.

Returning to the embodiment shown in FIG. 7, showerhead 706 and pedestal708 electrically communicate with RF power supply 714 and matchingnetwork 716 for powering a plasma. In some embodiments, the plasmaenergy may be controlled by controlling one or more of a process stationpressure, a gas concentration, an RF source power, an RF sourcefrequency, and a plasma power pulse timing. For example, RF power supply714 and matching network 716 may be operated at any suitable power toform a plasma having a desired composition of radical species. Examplesof suitable powers are included above. Likewise, RF power supply 714 mayprovide RF power of any suitable frequency. In some embodiments, RFpower supply 714 may be configured to control high- and low-frequency RFpower sources independently of one another. Example low-frequency RFfrequencies may include, but are not limited to, frequencies between 50kHz and 700 kHz. Example high-frequency RF frequencies may include, butare not limited to, frequencies between 1.8 MHz and 2.45 GHz. It will beappreciated that any suitable parameters may be modulated discretely orcontinuously to provide plasma energy for the surface reactions. In onenon-limiting example, the plasma power may be intermittently pulsed toreduce ion bombardment with the substrate surface relative tocontinuously powered plasmas.

In some embodiments, the plasma may be monitored in-situ by one or moreplasma monitors. In one scenario, plasma power may be monitored by oneor more voltage, current sensors (e.g., VI probes). In another scenario,plasma density and/or process gas concentration may be measured by oneor more optical emission spectroscopy sensors (OES). In someembodiments, one or more plasma parameters may be programmaticallyadjusted based on measurements from such in-situ plasma monitors. Forexample, an OES sensor may be used in a feedback loop for providingprogrammatic control of plasma power. It will be appreciated that, insome embodiments, other monitors may be used to monitor the plasma andother process characteristics. Such monitors may include, but are notlimited to, infrared (IR) monitors, acoustic monitors, and pressuretransducers.

In some embodiments, the plasma may be controlled via input/outputcontrol (IOC) sequencing instructions. In one example, the instructionsfor setting plasma conditions for a plasma process phase may be includedin a corresponding plasma activation recipe phase of a depositionprocess recipe. In some cases, process recipe phases may be sequentiallyarranged, so that all instructions for a deposition process phase areexecuted concurrently with that process phase. In some embodiments,instructions for setting one or more plasma parameters may be includedin a recipe phase preceding a plasma process phase. For example, a firstrecipe phase may include instructions for setting a flow rate of aninert and/or a hydrocarbon precursor gas, instructions for setting aplasma generator to a power set point, and time delay instructions forthe first recipe phase. A second, subsequent recipe phase may includeinstructions for enabling the plasma generator and time delayinstructions for the second recipe phase. A third recipe phase mayinclude instructions for disabling the plasma generator and time delayinstructions for the third recipe phase. It will be appreciated thatthese recipe phases may be further subdivided and/or iterated in anysuitable way within the scope of the present disclosure.

In some embodiments, pedestal 708 may be temperature controlled viaheater 710. Further, in some embodiments, pressure control fordeposition process station 700 may be provided by butterfly valve 718.As shown in the embodiment of FIG. 7, butterfly valve 718 throttles avacuum provided by a downstream vacuum pump (not shown). However, insome embodiments, pressure control of process station 700 may also beadjusted by varying a flow rate of one or more gases introduced toprocess station 700.

FIG. 8 shows a schematic view of an embodiment of a multi-stationprocessing tool 800 with an inbound load lock 802 and an outbound loadlock 804, either or both of which may comprise a remote plasma source. Arobot 806, at atmospheric pressure, is configured to move wafers from acassette loaded through a pod 808 into inbound load lock 802 via anatmospheric port 810. A wafer is placed by the robot 806 on a pedestal812 in the inbound load lock 802, the atmospheric port 810 is closed,and the load lock is pumped down. Where the inbound load lock 802comprises a remote plasma source, the wafer may be exposed to a remoteplasma treatment in the load lock prior to being introduced into aprocessing chamber 814. Further, the wafer also may be heated in theinbound load lock 802 as well, for example, to remove moisture andadsorbed gases. Next, a chamber transport port 816 to processing chamber814 is opened, and another robot (not shown) places the wafer into thereactor on a pedestal of a first station shown in the reactor forprocessing. While the embodiment depicted in FIG. 4 includes load locks,it will be appreciated that, in some embodiments, direct entry of awafer into a process station may be provided.

The depicted processing chamber 814 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 8. Each station hasa heated pedestal (shown at 818 for station 1), and gas line inlets. Itwill be appreciated that in some embodiments, each process station mayhave different or multiple purposes. While the depicted processingchamber 814 comprises four stations, it will be understood that aprocessing chamber according to the present disclosure may have anysuitable number of stations. For example, in some embodiments, aprocessing chamber may have five or more stations, while in otherembodiments a processing chamber may have three or fewer stations.

FIG. 8 also depicts an embodiment of a wafer handling system 890 fortransferring wafers within processing chamber 814. In some embodiments,wafer handling system 890 may transfer wafers between various processstations and/or between a process station and a load lock. It will beappreciated that any suitable wafer handling system may be employed.Non-limiting examples include wafer carousels and wafer handling robots.FIG. 8 also depicts an embodiment of a system controller 850 employed tocontrol process conditions and hardware states of process tool 800.System controller 850 may include one or more memory devices 856, one ormore mass storage devices 854, and one or more processors 852. Processor852 may include a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc.

In some embodiments, system controller 850 controls all of theactivities of process tool 800. System controller 850 executes systemcontrol software 858 stored in mass storage device 854, loaded intomemory device 856, and executed on processor 852. System controlsoftware 858 may include instructions for controlling the timing,mixture of gases, chamber and/or station pressure, chamber and/orstation temperature, purge conditions and timing, wafer temperature, RFpower levels, RF frequencies, substrate, pedestal, chuck and/orsusceptor position, and other parameters of a particular processperformed by process tool 800. System control software 858 may beconfigured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components necessary to carry out variousprocess tool processes in accordance with the disclosed methods. Systemcontrol software 858 may be coded in any suitable computer readableprogramming language.

In some embodiments, system control software 858 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. Other computer software and/orprograms stored on mass storage device 854 and/or memory device 856associated with system controller 850 may be employed in someembodiments. Examples of programs or sections of programs for thispurpose include a substrate positioning program, a process gas controlprogram, a pressure control program, a heater control program, and aplasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto pedestal 818and to control the spacing between the substrate and other parts ofprocess tool 800.

A process gas control program may include code for controlling gascomposition and flow rates and optionally for flowing gas into one ormore process stations prior to deposition in order to stabilize thepressure in the process station. The process gas control program mayinclude code for controlling gas composition and flow rates within anyof the disclosed ranges. A pressure control program may include code forcontrolling the pressure in the process station by regulating, forexample, a throttle valve in the exhaust system of the process station,a gas flow into the process station, etc. The pressure control programmay include code for maintaining the pressure in the process stationwithin any of the disclosed pressure ranges.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate. The heater control program may includeinstructions to maintain the temperature of the substrate within any ofthe disclosed ranges.

A plasma control program may include code for setting RF power levelsand frequencies applied to the process electrodes in one or more processstations, for example using any of the RF power levels disclosed herein.The plasma control program may also include code for controlling theduration of each plasma exposure.

In some embodiments, there may be a user interface associated withsystem controller 850. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 850 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF power levels, frequency, and exposure time), etc. Theseparameters may be provided to the user in the form of a recipe, whichmay be entered utilizing the user interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 850 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 800.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

Any suitable chamber may be used to implement the disclosed embodiments.Example deposition apparatuses include, but are not limited to,apparatus from the ALTUS® product family, the VECTOR® product family,and/or the SPEED® product family, each available from Lam ResearchCorp., of Fremont, Calif., or any of a variety of other commerciallyavailable processing systems. Two or more of the stations may performthe same functions. Similarly, two or more stations may performdifferent functions. Each station can be designed/configured to performa particular function/method as desired.

FIG. 9 is a block diagram of a processing system suitable for conductingthin film deposition processes in accordance with certain embodiments.The system 900 includes a transfer module 903. The transfer module 903provides a clean, pressurized environment to minimize risk ofcontamination of substrates being processed as they are moved betweenvarious reactor modules. Mounted on the transfer module 903 are twomulti-station reactors 909 and 910, each capable of performing atomiclayer deposition (ALD) and/or chemical vapor deposition (CVD) accordingto certain embodiments. Reactors 909 and 910 may include multiplestations 911, 913, 915, and 917 that may sequentially ornon-sequentially perform operations in accordance with disclosedembodiments. The stations may include a heated pedestal or substratesupport, one or more gas inlets or showerhead or dispersion plate.

Also mounted on the transfer module 903 may be one or more single ormulti-station modules 907 capable of performing plasma or chemical(non-plasma) pre-cleans, or any other processes described in relation tothe disclosed methods. The module 907 may in some cases be used forvarious treatments to, for example, prepare a substrate for a depositionprocess. The module 907 may also be designed/configured to performvarious other processes such as etching or polishing. The system 900also includes one or more wafer source modules 901, where wafers arestored before and after processing. An atmospheric robot (not shown) inthe atmospheric transfer chamber 919 may first remove wafers from thesource modules 901 to loadlocks 921. A wafer transfer device (generallya robot arm unit) in the transfer module 903 moves the wafers fromloadlocks 921 to and among the modules mounted on the transfer module903.

In various embodiments, a system controller 929 is employed to controlprocess conditions during deposition. The controller 929 will typicallyinclude one or more memory devices and one or more processors. Aprocessor may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.

The controller 929 may control all of the activities of the depositionapparatus. The system controller 929 executes system control software,including sets of instructions for controlling the timing, mixture ofgases, chamber pressure, chamber temperature, wafer temperature, radiofrequency (RF) power levels, wafer chuck or pedestal position, and otherparameters of a particular process. Other computer programs stored onmemory devices associated with the controller 929 may be employed insome embodiments.

Typically there will be a user interface associated with the controller929. The user interface may include a display screen, graphical softwaredisplays of the apparatus and/or process conditions, and user inputdevices such as pointing devices, keyboards, touch screens, microphones,etc.

System control logic may be configured in any suitable way. In general,the logic can be designed or configured in hardware and/or software. Theinstructions for controlling the drive circuitry may be hard coded orprovided as software. The instructions may be provided by “programming.”Such programming is understood to include logic of any form, includinghard coded logic in digital signal processors, application-specificintegrated circuits, and other devices which have specific algorithmsimplemented as hardware. Programming is also understood to includesoftware or firmware instructions that may be executed on a generalpurpose processor. System control software may be coded in any suitablecomputer readable programming language.

The computer program code for controlling the germanium-containingreducing agent pulses, hydrogen flow, and tungsten-containing precursorpulses, and other processes in a process sequence can be written in anyconventional computer readable programming language: for example,assembly language, C, C++, Pascal, Fortran, or others. Compiled objectcode or script is executed by the processor to perform the tasksidentified in the program. Also as indicated, the program code may behard coded.

The controller parameters relate to process conditions, such as, forexample, process gas composition and flow rates, temperature, pressure,cooling gas pressure, substrate temperature, and chamber walltemperature. These parameters are provided to the user in the form of arecipe, and may be entered utilizing the user interface. Signals formonitoring the process may be provided by analog and/or digital inputconnections of the system controller 929. The signals for controllingthe process are output on the analog and digital output connections ofthe deposition apparatus 900.

The system software may be designed or configured in many differentways. For example, various chamber component subroutines or controlobjects may be written to control operation of the chamber componentsnecessary to carry out the deposition processes (and other processes, insome cases) in accordance with the disclosed embodiments. Examples ofprograms or sections of programs for this purpose include substratepositioning code, process gas control code, pressure control code, andheater control code.

In some implementations, a controller 929 is part of a system, which maybe part of the above-described examples. Such systems can includesemiconductor processing equipment, including a processing tool ortools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. The electronics may be referred to asthe “controller,” which may control various components or subparts ofthe system or systems. The controller 929, depending on the processingrequirements and/or the type of system, may be programmed to control anyof the processes disclosed herein, including the delivery of processinggases, temperature settings (e.g., heating and/or cooling), pressuresettings, vacuum settings, power settings, radio frequency (RF)generator settings in some systems, RF matching circuit settings,frequency settings, flow rate settings, fluid delivery settings,positional and operation settings, wafer transfers into and out of atool and other transfer tools and/or load locks connected to orinterfaced with a specific system.

Broadly speaking, the controller may be defined as electronics havingvarious integrated circuits, logic, memory, and/or software that receiveinstructions, issue instructions, control operation, enable cleaningoperations, enable endpoint measurements, and the like. The integratedcircuits may include chips in the form of firmware that store programinstructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing steps during thefabrication of one or more layers, materials, metals, oxides, silicon,silicon dioxide, surfaces, circuits, and/or dies of a wafer.

The controller, in some implementations, may be a part of or coupled toa computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller receives instructionsin the form of data, which specify parameters for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters may be specific to the type of process tobe performed and the type of tool that the controller is configured tointerface with or control. Thus as described above, the controller maybe distributed, such as by comprising one or more discrete controllersthat are networked together and working towards a common purpose, suchas the processes and controls described herein. An example of adistributed controller for such purposes would be one or more integratedcircuits on a chamber in communication with one or more integratedcircuits located remotely (such as at the platform level or as part of aremote computer) that combine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber ormodule, a deposition chamber or module, a spin-rinse chamber or module,a metal plating chamber or module, a clean chamber or module, a beveledge etch chamber or module, a physical vapor deposition (PVD) chamberor module, a chemical vapor deposition (CVD) chamber or module, anatomic layer deposition (ALD) chamber or module, an atomic layer etch(ALE) chamber or module, an ion implantation chamber or module, a trackchamber or module, and any other semiconductor processing systems thatmay be associated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

CONCLUSION

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications may be practiced within the scope ofthe appended claims. It should be noted that there are many alternativeways of implementing the processes, systems, and apparatus of thepresent embodiments. In other instances, well-known process operationshave not been described in detail to not unnecessarily obscure thedisclosed embodiments. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

1. A method of forming an ashable hard mask (AHM) film, comprising:exposing a semiconductor substrate to a process gas comprising ahydrocarbon precursor gas and helium gas, substantially without anyother inert gas; and depositing on the substrate an AHM film by a plasmaenhanced chemical vapor deposition (PECVD) process, wherein the processcomprises: igniting a plasma generated by a dual radio frequency (RF)plasma source including a high frequency (HF) component and a lowfrequency (LF) component; the HF power is constant during deposition,and the LF power is pulsed, with at least about 3000 W per 300 mm waferand a duty cycle between about 10% and about 75%.
 2. The method of claim1, wherein the hydrocarbon precursor gas comprises compounds having amolecular weight of at most about 50 g/mol.
 3. The method of claim 1,wherein the hydrocarbon precursor gas comprises compounds having a C:Hratio of at least 0.5.
 4. The method of claim 1, wherein the hydrocarbonprecursor gas comprises acetylene (C₂H₂).
 5. The method of claim 1,wherein the hydrocarbon precursor has a partial pressure between about1-2% of the process gas.
 6. The method of claim 1, wherein the LF poweris provided at a frequency of less than or equal to about 2 MHz.
 7. Themethod of claim 1, wherein the LF power is between about 3500 W andabout 6500 W per 300 mm wafer.
 8. The method of claim 1, wherein the LFpower is pulsed at a frequency of at least about 100 Hz.
 9. The methodof claim 1, wherein the LF power is pulsed at a frequency between about100 Hz and about 1000 Hz.
 10. The method of claim 1, wherein the LFpower duty cycle is between about 10% and about 50%.
 11. The method ofclaim 1, wherein the LF power duty cycle is between about 60% and about90%.
 12. The method of claim 1, wherein the LF power has an on periodfor a duration of between about 200 microseconds and about 300microseconds.
 13. The method of claim 1, wherein the method is performedin a multi-station reactor.
 14. The method of claim 1, wherein theinternal stress of the AHM film is at most about −1400 MPa.
 15. Themethod of claim 1, wherein the modulus of the AHM film is at least about80 GPa.
 16. The method of claim 1, wherein the density of the AHM filmis at least about 1.5 g/cm³.
 17. The method of claim 1, wherein thehydrogen concentration of the AHM film is at most about 25 atomicpercent.
 18. The method of claim 1, wherein the thickness of the AHMfilm is at most about 2500 nm.
 19. The method of claim 1, wherein a gapbetween the pedestal and the showerhead is less than about 20 mm. 20.The method of claim 1, further comprising patterning the deposited AHMfilm and etching the patterned AHM film to define features of the AHMfilm in the substrate.
 21. The method of claim 20, further comprisingetching layers in the substrate underlying the AHM film.
 22. A method offorming an ashable hard mask (AHM) film, comprising: exposing asemiconductor substrate to a process gas comprising a hydrocarbonprecursor gas and an inert gas; and depositing on the substrate an AHMfilm by a plasma enhanced chemical vapor deposition (PECVD) process,wherein the process comprises: igniting a plasma generated by a dualradio frequency (RF) plasma source including a high frequency (HF)component and a low frequency (LF) component; the HF power is constantduring deposition, and the LF power is pulsed, with at least about 3000W per 300 mm wafer and the LF power on time per duty cycle is less than300 microseconds.
 23. The method of claim 22, wherein the LF power dutycycle is between about 10% and 50%.
 24. The method of claim 22, whereinthe LF power on time is between 200 microseconds and 300 microseconds.25. The method of claim 22, wherein the LF power is pulsed at afrequency of at least 100 Hz.